Register Transfer Language

Each of MARIE’s instructions consist of a sequence of micro-operations: data movements between registers as well as arithmetic & logical operations.

The exact sequence of micro-operations that are carried out by an instruction can be specified using the register transfer language (RTL).

We use the notation $M[X]$ to indicate the actual data value stored in a memory location $X$, and $\leftarrow$ to indicate the transfer of bytes to a register or memory location.

Example RTL for the LOAD X instruction:

$$\begin{array}{rl}MAR& \leftarrow X\\ MBR& \leftarrow M[MAR]\\ AC& \leftarrow MBR\end{array}$$

Example RTL for the ADD X instruction:

$$\begin{array}{rl}MAR& \leftarrow X\\ MBR& \leftarrow M[MAR]\\ AC& \leftarrow AC+MBR\end{array}$$

Example RTL for the JUMP X instruction:

$PC\leftarrow X$